


the posterior probability

by izayas



Category: Haikyuu!!
Genre: Alternate Universe - Modern Setting, Getting Together, M/M, Single POV, Strangers to Lovers, eventual lowkey msby 4 shenanigans because omi always suffers, professor omi and resident atsumu and bad stats puns
Language: English
Status: In-Progress
Published: 2021-02-24
Updated: 2021-03-11
Packaged: 2021-03-14 10:14:13
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 16,361
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29665722
Author URL: https://archiveofourown.org/users/izayas/pseuds/izayas
Summary: “i’m supposed to believe that you’re a pediatric resident moonlighting as an undergraduate statistics student, spending your little free time attending my lectures for, what, fun?” sakusa asks. “lies should at least be believable.”atsumu’s nose wrinkles. “omi-kun, yer kinda rude. i’m not moonlightin’. i‘mlearnin’.”
Relationships: Miya Atsumu/Sakusa Kiyoomi
Comments: 54
Kudos: 178





	1. the face

**Author's Note:**

> my amazing and wonderful beta who i owe my life to: [loveandallthat](https://archiveofourown.org/users/loveandallthat)
> 
> when i said sakusa ruined my life, i really mean that he ruined my life. 
> 
> mentioned: iwaoi, bokuaka, osasuna, ushiten, komori/mao (there's no reason behind this i just think mao is really pretty)

Sakusa doesn't trust the blond student in his introductory statistics lecture.

He's a fair person. He's rational and realistic, rarely acts without a solid reasoning behind his actions. However, Sakusa's gut, which has kept him alive and well for his entire life so far, is telling him to not trust the blond student whose half-lidded eyes he keeps catching whenever he looks up and out, whose lips seem permanently etched in a smirk, who is honestly just sitting there quietly but somehow still creates a volcano of disruption. His gut is telling him to not trust him and if for forty seven out of fifty scenarios Sakusa has foolproof logic to support him, this is one of the three that doesn't.

As a professor, making eye contact with a student usually isn't a bad thing. Even for Sakusa, who doesn't enjoy even this bare minimum of social interactions, knowing his students are paying attention leaves him feeling satisfied.

Apparently, though, not with this one.

It might be the hooded eyes. It might be that despite attending almost every lecture, he hasn't once pulled out a laptop, notebook, or even a pen. It might be that _every single time_ he looks, the student's watching him, looking alert even though he's just sitting with his hands in his pockets and an ankle over his knee. It might be a combination of those things; Sakusa doesn't know. He doesn't know and it's driving him crazy because he hates not understanding something, but he's also in the middle of lecture and won't let one student deter him from teaching the rest of the significantly less annoying class.

"Bayes' Theorem," he says and taps the space key on his laptop to pull up the next slide, "calculates the probability of event A given event B." His voice carries easily through the large, mostly filled lecture hall. He's surprised at how many people attend a lecture where attendance isn't mandatory and for most professors, this would be an excellent conundrum.

For Sakusa, he's thinking about how many of these sniffling young adults have yet to get their flu shot.

Sakusa's the youngest professor in the statistics department, tied with Ushijima as the youngest to be hired at twenty-six. He knows this only because Meian tells him once and Komori repeatedly reminds him (as if Sakusa doesn't know his own age and profession.) He enjoys research and writing papers; the more social aspects of the job, such as lecturing and networking to secure funding, are absolutely his least favorite, but pursuing a path in academia has always been his plan, the way his sister's was opening her own law firm and his brother's was becoming an investment banking partner.

Ushijima's guidance makes his first semester bearable. When Komori tells him that he needs glasses now that he's a professor, Sakusa scoffs. Then he sits in on one of Ushijima's summer lectures, sees his friend who he knows to have twenty-twenty vision wearing a pair, and immediately goes to buy his own.

Sakusa is a realist, so he understands that he's been slotted into the introductory statistics lecture because he's a newcomer. He expects that as he gains experience and when he's no longer the newest faculty member, he'll be allowed higher level courses, ones whose curriculums may challenge him to prepare and deliver. Sakusa doesn't like to hope or expect, but, he finds, he really hopes that's the case and that in the near future, he'll have to stand in front of just twenty students who actively have an interest in statistics instead of up to two hundred trying to fulfill a requirement.

It's a given that he'll have to stand in front of students who may or may not have gotten their flu shots, but twenty is far, _far_ fewer people than two hundred.

He looks up, catches the blond's persistent gaze and frowns a little. Sakusa tries to go through a mental catalogue of his class roster, but he has almost two hundred students and even he hasn't memorized all of them in just a few weeks' time.

"A popular application concerns false positives and negatives on tests," he continues, glances at the clock as he pushes his black-rimmed glasses up the bridge of his nose. "For instance, what is the probability of a true positive, given the test has a 98% accuracy rate? Your homework involves proving the theorem as well as a few applications of it. As always, Kunimi-san and I are available at our individual office hours should you have questions."

Sakusa doesn't need to dismiss them. It takes just one person to see that it's time and as soon as they close their laptop, the domino effect fills the room, compounded by a harmony of zipping backpacks and chatters. Sakusa pushes off the desk and walks around it; one palm presses to the surface next to his computer as the other hand closes a few windows with the trackpad, takes a moment to frown at the lack of new emails. A soft _sensei?_ garners his attention and he glances up, nods. "Yes?"

"I just have a question about what you were covering, if that's all right."

Sakusa has errands to run, but he's actually _not_ an asshole, as he's heard acquaintances grumble under their breath. He just nods again and closes his laptop, straightening. He's listening to the question—it's a simple one, something she could technically figure out by reviewing the slides he sends out before every class—and adjusts his glasses. The blond is at the end of the line of three more students and when Sakusa's eyes land on him, his are downcast and on his phone.

He looks up, eyes hooded and brows dark, and smirks in a way that makes Sakusa frown.

She chirps a _thank you_ at his reply and Sakusa's dark eyes pick up the small blush dusting her cheeks. He asks if she's gotten her flu shot; she stares at him and nods hesitantly, laughs sheepishly. "It's because you remind all of us every lecture, actually."

He nods again in satisfaction because at least he can confirm her light flush isn't from a fever. She hurries off and the other's questions are among a similar vein; two of them also have a suspicious glow on their cheeks and the last student before the blond asks about enrollment capacity. Sakusa stares at him. "The class is full?" he asks and he nods.

"Yeah. I thought a few spots would open up, but nobody seems to be dropping."

Sakusa frowns. He opens his computer again to navigate to his class homepage and blinks to see that all two hundred seats are actually filled. His lips purse and he closes it again. "I'll speak to the department about increasing the enrollment cap. What's your name?"

"Oikawa Takeru," he says. Sakusa nods. The blond's head jerks up, stares at the back of Takeru's head for a few moments. He then smirks and looks back down, continues tapping on his phone. "I need this class for my major, so—"

"I understand. It shouldn't be an issue," Sakusa says. Takeru seems relieved and thanks him again. His backpack's supported by the strap on a single shoulder (Sakusa wonders about the state of his posture) and he hurries out after checking his phone, a small blue Argentinian flag pin catching the light.

The blond loiters and doesn't immediately step forward, seemingly still preoccupied with his phone, so Sakusa takes the opportunity to bring his leather satchel onto the desk. He's slipped his laptop inside when the other finally takes a step forward. "Yes?" Sakusa asks flatly. When he looks up, the blond's phone has been pocketed and he's smirking. "Do you have a question?"

"Blunt, aren'tcha?" he asks and Sakusa just blinks at his accent. After years of attending this university and a semester of teaching, he's used to the myriad of dialects that prove how the school attracts students from all over the country.

This one, though, is more prominent than most.

"Just got a question, if ya have some time, Sakusa-sensei."

Sakusa doesn't quite like the way he calls him _Sakusa-sensei_ , even if that is what he'd expect most students to address him as. His brow knits and he nods, pushes his glasses further up the bridge of his nose. "Of course," he says evenly, "if it's related to the lecture."

"Kinda. It's more of a general question 'bout Bayesian statistics, if that's all right," he says and Sakusa blinks. "I know we didn't cover that and prob'ly not gonna for an intro class, though, so if—"

"Go ahead," he interrupts. "I don't mind."

The blond seems pleased. Sakusa's not one to judge his student's fashion choices (what he cares most about is their effort in class), but he wonders what sort of a student wears pants like _those_. He's almost always in them; of the thrice a week lectures, Sakusa's seen him wear these scrub-like pants in most of them, street clothes in a few others, and, to his knowledge, he's only missed one class.

Sakusa doesn't like that he's paid this much attention and what makes it worse is that he's also paid enough attention to realize that he's older than most of the students. This isn't a bad thing; if he's older and has decided to return to finish his education, Sakusa respects and admires that dedication. He can find him annoying and respect him at the same time because, as it turns out, humans are often multifaceted.

It's the way he carries himself, Sakusa thinks. It's not the same youthful arrogance of an eighteen year old entering what most students think of as a four-year escape from studying and work; it's a more smug, confident arrogance that's born from age and experience. He's his age, Sakusa has a feeling, and because of that, he feels better about being annoyed by him.

His hoodie's zipped up, school logo emblazoned on his left breast and the outline of his knuckles visible through the pockets. "Bayesian stats," he says, tilts his head, "'s different from classical stats 'cause its probabilities are subjective, right?"

Sakusa nods. "Yes. In general, the difference between the two are that classical statistics considers probabilities to be the frequency of an occurrence, whereas in Bayesian statistics, it's a degree of belief."

"'kay," the student says, bobs his head. "Jus' so I understand, can I run an example by ya?"

Sakusa doesn't see a problem with that. "Of course."

"So, hypothetically," he says and the way his smirk widens instantly gives Sakusa a very, very bad feeling, "in classical stats, if I were t'ask you out, that probability's just gonna stay at fifty percent no matter what, yeah?"

Sakusa stares at him silently for several seconds and squints.

"…Even hypothetically, it would not be fifty percent," he answers monotonously.

The smirk just widens, accompanied with an infuriating head tilt that seems to just draw one corner of his lips even higher. "Aw, sixty? Yer makin' me blush, sensei."

Sakusa suddenly sees many problems all coalescing into the one humanoid shape standing in front of him.

"But in Bayesian stats, that probability would change, yeah? Dependin' if I were a student or not? Posterior probability and all that?" he continues and Sakusa can't help but scowl because he's mad that this example actually does illustrate the point. "If I asked you out as a student, it'd be zero. If I asked you out not as a student, it'd be higher."

"It's not guaranteed to be higher," Sakusa just barely keeps from snapping.

"Well, ya can't go below zero, sensei. Probabilities are limited between zero and one."

"It could remain as zero."

"It could also go up."

Sakusa glowers. The blond grins; he pulls his hands out of his pocket and holds them up defensively. "Right, right, sorry. Just the best example I could think of on the spot; I'm not tryna get ya fired or anythin'. But that's the concept, right?"

Sakusa glares for another moment and then sighs again, knitting his brow and pinching the bridge of his nose right beneath his glasses. Komori's asked a few times if anyone's asked him out; he always repeats no, that it's absolutely against school rules and he would never consider being with someone who so flagrantly dismisses consequences and all Komori asks is, _"How many times?"_

Some people are more subtle than others and most bother to wait until the semester has ended. The semester isn't even a month in and Sakusa isn't sure how much more obvious one can get without just blatantly going against policy.

"…It's an application," he says at last and looks up after adjusting his glasses again, eyes narrowing. "One that's in poor taste to present to your professor, but yes."

"C'mon, said it was hypothetical, didn't I?" he says again and shrugs. "But thanks for yer time. Helps a lot."

He turns and starts heading towards the stairs; Sakusa can't explain how he knows, but it's an absolute truth that the blond knows he's watching him leave and is smugly smirking about it. Drumming his fingers along his arms, he clears his throat. "I actually have something I wanted to speak to you about," he says.

The student has a foot on the first step but stops and looks over his shoulder. "Hm?"

"You never take notes," Sakusa states, frowning.

The student blinks. A few more seconds pass before he goes, "Oh, was that it?" He shrugs. "Honestly, sensei, I'm not a stats student. More into biochem. I'll take notes when it gets tougher, don'tcha worry."

"Biochemistry?" Sakusa echoes. "This is a required class for that major?"

"Didn't say that," he answers airily and turns again, holds up a hand. "See ya next class. If ya bring up hierarchical modelin', I promise to take notes."

Sakusa doesn't bother to return that remark with an answer because not only would that be an irresponsible move as a professor to take his class from conditional property to hierarchical modeling while skipping posterior distributions, but he also wonders if it's coincidence the blond's mentioned the exact topic his dissertation had been about. He waits until he's gone; Sakusa ends up watching him amble up the stairs, hates that when he glances over his shoulder with one last smirk, they make eye contact.

The door closes and that's when Sakusa allows a true frown to tug at his lips. He opens his satchel and pulls out his computer, lifts the cover and impatiently taps the trackpad until it springs to life. He navigates to his roster and scrolls through all two hundred ID pictures and names. When he sees nothing, he switches to another view that includes their majors, if they've declared it, and doesn't see biochemistry. He switches back to the view with the pictures, just to make sure he didn't miss him the first time.

Sakusa's incredibly thorough and yet he _still_ doesn't see the face. He checks again, just for good measure, and when he's confirmed that the inexplicably annoying biochemistry student who proposes inappropriate but theoretically correct examples to his professor doesn't exist in his roster, Sakusa openly scowls and closes his laptop.

Teaching is _easily_ the worst part of this job.

* * *

Meian has been ignoring his email for seventy-two hours, and so Sakusa decides to confront him about it.

Sakusa knows that as an assistant professor, his time is split among various tasks; he can't spend all his time focusing on his next paper, but Sakusa also thinks the student organization and number of graduates that Meian's assigned him is a _little_ bit ridiculous. Meian himself has said that his dissertation was well-received and he's looking forward to what he publishes next; they have the same goal, he thinks, which is for him to publish, so he's not sure why Meian gave him three graduate students when even one is pushing his limits.

 _"There's no rush,"_ Meian says when Sakusa asks if he's seen his email and his proposal. He says he has and thinks it's an interesting topic with plenty of potential, just as he expects from Sakusa. _"The deadline for that is still a ways off, isn't it? You're early in your career, Sakusa-san. I understand the pressure to publish, but this isn't your sole priority; it's important to become well-rounded. Take a break from researching. Focus on your curriculum, spend some time reviewing your graduate students' proposals, it could inspire you. I don't want you to overwhelm yourself—"_

 _"I won't,"_ Sakusa reassures, but Meian doesn't seem convinced and Sakusa leaves the office more frustrated than when he arrived.

It's not in his nature to outwardly show his annoyance and he thinks that's why Yachi squeaks when he responds to her call of his name. It takes him a moment to relax his expression and he apologizes quietly, shakes his head when she asks if something's wrong. He remembers to ask her if she's able to increase the enrollment cap on his class; she answers if he's fine with it, she can allow all the waitlisted students to be enrolled and he nods.

_"Are you sure, Sakusa-san? I don't want you to be overwhelmed—"_

Sakusa twitches because he's a little tired of people trying to decide his boundaries for him, but manages to keep his composure because Yachi never has ill intent and she's one of the few people he truly, genuinely likes. He reassures her and after confirming that Takeru is one of the students to be enrolled, nods at a standing dinner invitation and leaves the office.

Sakusa doesn't make career influencing decisions without serious consideration. He's fully aware of the wide breadth of responsibility that befalls a professor, just how much the position differs from one focused on research. It's why every month he has to oversee a recreational go club, which he's only required to attend due to the technical requirement. It's why he has a list of recommendation letters to write already after just one semester (he's declined all but four but it's still four to write). It's why he has so many grant proposals to peer review that even for someone who normally enjoys reading, Sakusa's head is spinning a little.

But when his head's spinning, Sakusa takes a deep breath and makes himself a cup of tea, waits for it to stop spinning so he can get back to work. He knows better than to overwork himself; Sakusa can count on one hand the number of times he's slept less than his optimal seven hours, and all of them were because of extenuating circumstances. He chastises Komori whenever he sees him send a text well past 2 a.m. and grimaces when his graduate students send emails around sunrise.

The three graduate students he's been assigned are Kunimi, Goshiki, and Koganegawa. Goshiki and Koganegawa are much more proactive about their studies; Sakusa gets at least a few emails from each of them every week, some simple status updates he needn't reply to and others messages that he figures he should answer before they really start panicking. Kunimi's much more mellow and while Sakusa appreciates that, he's also not sure if he approves of his frequent 4 a.m. submissions of his drafts and the 3 a.m. timestamps of grade uploads to the course website. The work is fine but Sakusa can only wonder about his sleep schedule and overall physical health.

One time he emails him at 6:30 a.m. The next time he sees him in person, Sakusa notes that he hadn't expected Kunimi to be an early riser. Kunimi replies that he never slept.

Sakusa is horrified.

Glancing up to confirm he's at Onigiri Miya, Sakusa readjusts his satchel and fishes out a handkerchief to open the door with. He hears a bell and a bright _welcome!_ as soon as he enters; nodding, he folds the handkerchief, side touching the handle on the inside, and pockets it, comes to a stop and scans the menu.

He's here at Bokuto's recommendation because apparently Bokuto's newest client's twin brother owns the Osaka-born chain that's successful enough to open a Tokyo branch. Sakusa makes it a point to work out regularly no matter what his schedule is like and what he thinks is a one time _mind spotting me?_ turns into a reluctant friendship with the most popular trainer at the gym. Sakusa's since moved and now goes to a different gym but before that's happened, he's reluctantly dragged into a friendship with Bokuto and Akaashi, a literature fellow at the same university who Sakusa gets along with immediately.

It takes almost four months for Sakusa to admit Bokuto is a friend, largely driven by how fastidiously he follows every single safety protocol no matter how busy he is. The day Sakusa tells him he approves of his adherence to proper gym etiquette is the first and only time Bokuto tries to hug him, rejection mellowed by Sakusa finally giving him his phone number to start a group chat among the three.

Sakusa's reviewed Onigiri Miya's most recent health inspection online and is satisfied with the result. He also appreciates that the printed out menu he's looking at and the one online that he studied are the same, shows attention to detail and timely updates.

"What would you like? The owner's here today with some new flavors if you'd like to try those!" the girl behind the counter asks when he approaches, smiles cheerfully.

"That's all right. Just two umeboshi onigiri," he answers, speaks clearly so that she can understand despite his mask. The small store's pleasantly crowded, which Sakusa takes as a good sign. She beams and nods; Sakusa hands her his card and after she's finished the transaction, hands it back to him with both hands and asks him to wait, that it shouldn't take long.

Nodding, he steps back into the waiting area and pulls out his phone. As expected, there's no email from Meian, no _I've changed my mind, please devote all your time to research, Sakusa-san._ There's a text from Yachi asking if he's free next Tuesday evening; Sakusa checks his calendar, answers that he is. Komori's asked what the best way to get curry out of a white shirt is and Sakusa says to use a bib.

Komori's response is immediate.

**From: Motoya**

_huh? hows a bib going to get out a stain?_

**To: Motoya**

_Use a bib to avoid a stain._

**From: Motoya**

_funny. seriously i have a date tonight_

**To: Motoya**

_Buy a new shirt._

**From: Motoya**

_i don't have time today, swamped at work. just bring me one of yours_

**To: Motoya**

_No._

Komori sends back an emoji that Sakusa ignores. He finishes checking his text messages and pockets his phone, looks around the shop again. He's not the type to listen to people's suggestions very seriously but if there's one thing Bokuto's proven, it's that both he and Akaashi are incredibly serious about food. They seem to go on dates at least weekly and even make trips to Osaka often if a new restaurant has opened and is creating buzz. Even after being friends with them for months, it's hard for Sakusa to see how these two seemingly opposite personalities are together, but Sakusa supposes that once he gets past Bokuto's lack of volume control, he sees the warmth and charm that Akaashi's probably drawn to.

Sakusa asks how long they've been dating, just to be polite. Bokuto says forever. Akaashi says since high school. Bokuto then asks Sakusa if he's seeing anyone and when he says no, his eyes sparkle and he leans over the table at the restaurant they'd been having dinner at.

_"You want me to set you up, Omi-Omi? Remember my client whose twin owns Onigiri Miya? He's a good kid and single too!"_

Sakusa declines and Akaashi pats Bokuto's back soothingly when he visibly deflates.

Sakusa's never had much of an interest in dating. He's had a few short-lived, casual relationships that he's never been very broken up over. He's used to being by himself; until Komori started to hang out with him, his childhood was spent mostly in silence. His parents were largely overseas and his much older siblings were studying when he was a toddler, finishing their degrees when he was a teenager, and now well into their careers as he's properly starting his own. His relationship with his family has always been distant and because that's all he's ever known, when people ask if he's lonely he answers _no_ and looks at them quizzically.

He doesn't see a need to date someone, especially when his focus is on his career. He does perfectly fine on his own. He always has, and he doesn't see that changing in the future, doesn't know why he would put himself through the stress that Komori seems to go through almost cyclically with every new relationship. His last break-up had been with a boyfriend of two years, his longest and most serious relationship yet. It happened a few months ago and though Sakusa usually likes to spend his weekends relaxing at home, he shows up at Komori's apartment with take-out and a monotonous announcement that he's caught up on Komori's current favorite drama, so they can watch the new episode because even though Komori says he's fine, Sakusa hears the wobble in his voice through the phone.

Sakusa isn't a total asshole, honestly.

He's currently dating a barista, Sakusa thinks. He's mentioned her a few times and until they're serious enough that Komori introduces them or he's visibly upset over something, Sakusa decides to not pay much attention to their budding relationship.

"Here you go, Sakusa-san!"

Sakusa nods, sees the same girl from earlier standing at the edge of the counter smiling brightly. She's holding the twine handles of the bag with one hand, the other supporting the bottom. As he steps forward, a man emerges from the doorway behind her, holding a clipboard; he lazily drawls, "Michimiya-san," but stops at seeing Sakusa approach. "Ah. Yer with'a customer, sorry."

Sakusa's taking the bag from her as the man lifts the black cap he's donning and nods towards him. "Thanks 'nd hope ya enjoy."

Sakusa spent about ten minutes scrolling through two views of a roster looking for a face that is now in front of him and he feels like he's in a nightmare.

It's the exact same face, Sakusa thinks. It's not just that they bear a resemblance or that Sakusa's projecting his own annoyance; it's _literally the same face_ staring back at him, the dark brows and hooded eyes. This version of the face is framed with black hair and the lack of a smirk makes it more tolerable but, still, _it's the same face_ and Sakusa feels like he's in an alternate universe.

He just stares and _the face_ stares back. Sakusa remembers the girl mentioned the owner's here; is he the owner? Sakusa thinks with horror. He starts putting together all the facts he has:

 _The face_ is the same face of the annoying student who haunts Sakusa's already unenjoyable thrice-a-week lectures.

Bokuto has said the owner of Onigiri Miya is his client's twin.

Sakusa assumes that by twin, Bokuto means identical twin.

It is very rare for two unrelated people to have _the exact same face._

Bokuto wanted to set him up with this client.

The only fact that he doesn't have enough empirical evidence to confirm is also the one that would make or break his nausea-inducing conclusion and if _the face_ ends up not being the owner of Onigiri Miya, Sakusa can chalk this up to one horrible, horrible coincidence.

"Miya-san, do you need something?"

He's definitely the owner, Sakusa realizes and wonders when Bokuto started to hate him.

 _The face_ turns to the girl, hands her the clipboard and mentions needing help with inventory. She nods and hurries to the back and he straightens, adjusts his cap and levels Sakusa's gaze evenly; he's not smirking but his gaze holds the same sort of intensity as the blond's and Sakusa wonders how they have the same face but only one is ridiculously infuriating.

Sakusa thinks that his two umeboshi onigiri were not worth the stress he suddenly feels.

"Ya need somethin'?" he asks, frowns a bit.

Sakusa blinks one more time and shakes his head, deciding his energy is better spent on confronting Bokuto about the state of their friendship instead of giving the annoying student any additional thought. It's ironic, he thinks, that Bokuto suggested Onigiri Miya out of apparent kindness of his heart and it's where Sakusa realizes he hates him.

"No," he answers and the other nods, calls _have a good day_ in the hauntingly same accent as Sakusa leaves the shop, almost forgets to use his elbow to open the door.

He heads towards the subway station to go home, feet tracing a memorized path that his mind doesn't need to pilot. He takes out his Suica and taps it against the turnstyle impatiently, keeps his eyes laser-focused as he navigates through the station. It's only when he's on the platform and waiting in the least busy line that he pulls out his phone calmly. He takes a moment to adjust his mask until it's snug over the bridge of his nose and pulls up his group chat with Bokuto and Akaashi because they're basically one entity to him and this way he only has to say it once.

He's doing everything he can to focus all on assessing whether or not his friendship with Bokuto is at its end and hates that even now, a part of him can't help but think about the blond and feel like he's _won_ a competition that Sakusa didn't realize they were partaking in.

He scowls and composes a text.

**Sakusa Kiyoomi:** _Bokuto, if you don't want to be friends, just tell me._

It's lunchtime, so he's not surprised when the responses are immediate.

**Akaashi Keiji:** _Bokuto-san, what have you done?_

**Bokuto Kotaro:** _?? omi-omi? what????_


	2. lunch dates

**Summary for the Chapter:**

> sakusa regrets his whole entire life.

Sakusa hates that the onigiri is delicious because he can never go back to Onigiri Miya.

A few days have passed. The blond whose surname is most likely _Miya_ shows up a few minutes late to one of the lectures; his unofficial self-assigned seat is available and Sakusa can't help the reflex to look up at the door opening. He smirks as he sits, eye contact unwavering while he pulls a tiny flip notebook and pen out of his pocket and holds it up smugly.

Sakusa barely resists the urge to storm up the stairs and kick him out. He's normally very calm and composed, so he doesn't know why this single student irks him so much.

(He says this to Komori, who laughs at _calm and composed_ and Sakusa decides it better not to ask for clarification.)

Today's one of the two days a week he doesn't have class and Sakusa's been emailed another proposal to peer review. Kunimi's also sent him a first draft of what he has for his dissertation (time stamped at 7:14 a.m. which Sakusa has a feeling is the result of never sleeping instead of waking early) and he's expecting Koganegawa to send over some revisions by the end of the day. He also has lecture notes to review and some administrative duties related to his class, but those aren't nearly as grating because it's hard for Sakusa to not feel irked that it seems everyone around him is allowed to focus on research and he's the only one who can't.

"Where are you anyway? It's kind of loud and you don't normally call from the café."

"The one I usually go to is closed," Sakusa answers, angles the way he's holding his phone so the speaker's closer to his mouth. He adjusts the wireless earbud he's wearing. "I'm at the one at the hospital."

"The hospital, for real?" Komori asks with a laugh. "Their coffee sucks."

"It's passable." Komori's a coffee expert, his journey starting as a result of college because double majoring in astronomy and astrophysics seems like a sure fire way to obliterate any chance of a normal sleep schedule. Komori tends to stay up so late that coffee shops have long since closed and when he starts brewing his own coffee, his focus is caffeine. Unfortunately, Komori doesn't like bitterness and so that's when he begins to look into how to brew _good_ coffee that's still strong, splurging on beans and machines and though Sakusa tells him he's full of shit and wasting his trust fund, he hates that the cup Komori brews him actually is delicious. The chains on campus turn Komori's nose upwards and he never fails to grimace when Sakusa shows up with one of their cups, fingers curled around a paper sleeve.

_"Don't you have tastebuds, Kiyoomi?"_

_"Yes, but no time to care."_

He always looks Komori in the eye as he takes a long, gratifying sip.

Sakusa knows good coffee. He spends so much of his free time with Komori (or, rather, Komori tags along when he has free time) that he's dragged onto this coffee exploration journey during their undergraduate years after growing up surrounded by some of the best that money can buy. But, at the same time, Sakusa has work to do; even if the hospital's watered down americano doesn't taste good, it has caffeine and that's all Sakusa needs. He has too much to do to justify making the trip to a specialty shop in Minato just because the flavor is richer and less acidic.

Komori audibly groans when Sakusa mentions he has an americano, so he purposely jostles the cup to make sure Komori hears the ice clink against each other.

"What did you want to talk about?" Sakusa asks. He takes a sip of his coffee, eyes never leaving his screen.

"Oh, nothing. Just wanted to catch up. If it's not a good time we can talk later."

Sakusa blinks.

Komori doesn't say anything.

Sakusa frowns.

"…Okay, fine," Komori sighs, "my mom called and mentioned your mom called you. I'm making sure you're okay. Looks like she's making rounds on her kids to make sure they're living up to the Sakusa name."

Sakusa sets the plastic cup down onto a folded napkin to catch condensation. "She didn't call me," Sakusa answers.

"Oh." Komori sounds surprised.

"She emailed a seven-paragraph message to update me on my siblings' accomplishments."

"Oh." Komori doesn't sound surprised.

Sakusa takes a moment, reads the first paragraph and already has a comment to make. He and Komori are cousins; their mothers are sisters, but their families are entirely different. As much as Sakusa isn't close with his immediate family, Komori's close with his, though because of how much he and Sakusa spent time together when younger, he's said that he considers himself to be closer to Sakusa than either of his sisters. Sakusa hadn't said anything, just adjusted his mask and Komori laughed because, unfortunately, Komori knows him well enough that even a mask can't cover the expression he's trying to hide.

He waits until he's finished typing a scathing note that he highlights as a reminder to have Komori reword to something softer. "It's fine," Sakusa says, knows that if he's silent for any longer, Komori might show up and that'll just make it harder to focus. "She's just asked when I'll publish my next paper, which is a fair question."

"You literally _just_ —"

"Don't misuse literally. I've spoken to Meian to express my desire to focus on research soon. If he won't allow me, I'll at least ask to devise my own curriculum for a course next year."

Komori doesn't sound relieved at all to hear what Sakusa thinks is the most practical plan he could have come up with. "You're not working too hard, are you?"

Sakusa blinks. "I sleep seven hours a night and make sure I'm obtaining all of the daily—"

"Kiyoomi," Komori interrupts and the only reason Sakusa doesn't frown more is because Komori _knows_ how much he hates to be interrupted. "I know you take care of yourself, but just because you're sleeping and eating well and doing all your work doesn't mean you're okay."

"Of course it does," he replies impatiently.

"No, it doesn't," Komori sighs. "Why don't we get dinner? You want to meet Aihara-san?"

"Not particularly."

"Okay, well you'll have to meet her eventually, so it might as well be tonight—"

"I have work to do," Sakusa says, voice even. "I'll meet her when—"

"You're never not busy," Komori says and this time Sakusa frowns because it's the second interruption in under five minutes. "If you have any free time, you're just using it to work more and you schedule your breaks so strictly that I'm pretty sure you're not actually relaxing. You have to make time for yourself; I'm worried about you."

"You don't need to be," Sakusa answers a bit more sharply than he intended and when the webpage doesn't load immediately, his brow knits and he hits refresh. "We're not children anymore. Your mom isn't asking you to look after me."

"You think I only care about you because someone told me to hang out with you almost two decades ago?"

Sakusa blinks. The page has loaded but his fingers remain suspended over the trackpad, even when a window pops up and warns him that he'll be logged out because of inactivity. Komori's silence has his frown deepening and he drops his eyes, mumbles _no_ in a low voice and Komori gives a frustrated sigh.

Komori had been his only friend growing up and even though they started hanging out because of Komori's mother telling him to, by the time they were in middle school and high school, Komori's effervescent personality made him easily popular. He had every chance to drop Sakusa but he never did; Sakusa's aware he's not the easiest person to befriend, has a feeling that some of Komori's new "friends" probably told him he'd be even more popular if he didn't steadfastly stick by his cousin's side. Komori never once even began to pull away, though; he made sure that if he was invited somewhere that Sakusa was also extended an invitation even if he never went.

Pressing his lips into a thin line, he exhales silently through his nose and closes his eyes. "…I can do dinner tonight," he says quietly, "to meet Aihara-san."

It's quiet for a moment. Sakusa stares at his screen without quite looking at anything; he's wondering if Komori's mad enough that he actually has to verbally apologize but when he hears the heavy sigh crackle through his phone, Sakusa's shoulders visibly lower, eyes half-lidded as they focus on his screen to log back into his class website.

"About time. You might even like her. She teases me about my eyebrows sometimes, but in a cute way. She also straightens my collar and keeps a lint roller in her purse. You two can bond over that."

"It's good to be prepared."

Komori laughs at that and Sakusa relaxes, fingers moving to the trackpad navigating to his roster. He sees that there are now two hundred and twelve students; he's informed Kunimi of this and he just sighed but nodded.

_"The midterm is going to be scantron, right?"_

_"And free response."_

Kunimi looked like Sakusa informed him he just ran over a precious childhood pet.

"She has a friend," Komori says after a pause and Sakusa blinks. "I can ask if—"

"I'm not interested in dating," he says flatly and can almost see the way Komori frowns. "You know that. Stop trying to set me up."

"I'm worried," Komori says and Sakusa's brow knits. He lowers his phone as he takes a sip of his coffee, keeps the phone where it is even after setting the cup back down. "I know you're fine on your own and you're independent by nature. You've always been. But I don't want you to be so steadfast in that that you miss meeting someone who would make you happy."

"I'm _fine_ ," Sakusa repeats, taps a bit harder on his trackpad than he means to and furrows his brow.

"I know you're fine," Komori repeats patiently, "because you plan ahead and prepare for everything. But you shouldn't live your entire life being just fine and only focusing on what's practical—"

"Motoya."

Komori pauses. Sakusa's about to hang up if he tries to push the topic; he's done it before because Sakusa has strict boundaries that Komori sometimes tries to push his luck with. He thinks this might be another one of those times until he hears a heavy sigh and moves his thumb, away from the red button.

"Fine. Forgot how stubborn you can be sometimes."

Sakusa doesn't grace that with an answer.

The coffee shop is starting to get busier; Sakusa supposes _coffee shop_ is a bit generous for what's best described as a small stand with outdoor seating. In the winter, the stand closes and the vendor moves to a cart inside the lobby, where there's no seating, save some benches. Glancing at the corner of his screen, he confirms that the exponentially increasing number of patrons is from the lunch rush. "Have you decided where to go for dinner?" he asks after almost an entire minute of silence has elapsed.

"Well, now that you're coming, I'll be sure to text you a place and time with at least two hours' notice. Aihara-san and I usually decide when we meet up."

"Only two?" Sakusa asks with a frown.

"Kiyoomi."

He's still frowning but concedes at Komori's warning tone. "Fine."

Komori's quiet again. Sakusa's finished his coffee and has momentarily set his phone on the table so that he can pull his mask back on as the area fills with scrubs and white coats; while on one hand he has faith in their personal hygiene, they're also doctors surrounded by patients all day. He frowns behind his mask when he hears Komori's voice again; it's not that he wants his cousin to be overworked at JAXA, but he does wish his lunch breaks weren't so long.

"You spent a lot of time by yourself when we were kids, especially before we started hanging out."

"Yes," Sakusa answers flatly. "I'm aware. I was there."

"I'm not trying to nag or be a second mom to you," Komori continues and Sakusa's lips arch downwards even further behind the security of his mask, "but because you're fine now doesn't mean that's how it has to be forever. If you find someone, you also shouldn't push them away just because it's not something that you think is necessary or gets in the way of work."

Sakusa blinks. Komori says that his lunch break is about over and he has to leave. Sakusa mumbles _all right_ and is still staring at the same spot on his computer when they hang up. He sets his phone down and teases the earbud out, takes a moment to clean it with a sanitizer wipe before returning it to its case. He wipes his phone down for good measure as well and then as much of the table as he can before folding up the dried sheet, leaving it to the side.

Komori's technically older but eight months don't offer significant life experience, and yet, every once in a while he'll impart life wisdom like he's lived decades longer than Sakusa has. Komori's one saving grace is that he actually _knows_ Sakusa because he's grown up with him and has taken the time to know him; it's the only reason why Sakusa will occasionally put weight into his words instead of trying to brush them off like he does with his parents or siblings.

It doesn't mean he likes it, though.

Sakusa tries to go back to reading; once the lunchtime rush dies down, he'll get another coffee, he decides. He trains his eyes on the screen; now that he's off the phone, he's maximized the proposal but even so, he barely gets three sentences in because he sees the word _Bayesian_ and immediately thinks of _Miya._

Sakusa could probably find out his first name if he tried, but he doesn't care to and just knowing his surname is more information that he wants. Even though he hasn't come up to him after class again, his presence has grown even more irritating and Sakusa doesn't understand how in a lecture hall with over two hundred seats, the back left seems to always be the one his eyes are drawn to and how _Miya_ is always sitting there.

Smug, Sakusa thinks, is the perfect way to describe him. It's the way he carries himself and the way he smirks; there's an _I'm better than you_ aura around him that Sakusa doesn't like. He never speaks during lecture and despite his tiny little notebook, Sakusa's still never seen him write anything down, pen moving only between his breast pocket and his lip. He has no idea if he's actually retaining the information because for all he knows, he could've just done a quick internet search on what Bayesian statistics was and gotten lucky.

It still begs the question how he knew about hierarchical modeling and if it was a coincidence or he knew that's what Sakusa's dissertation had been on.

Sighing, Sakusa rubs the right side of his forehead tiredly. He definitely needs another coffee immediately, badly enough that he'll deal with the line. His normal seven hours of sleep have dipped to five as of late because though he does his part in going to bed on time, insomnia chips away at his intentions. A hand rests over the edge of his computer in preparation to close it as he prepares to stand when he notices two more doctors walking out, both wearing blue scrubs.

It's a common shade of blue; he's seen it donned on so many people today that Sakusa has no idea why _these_ blue scrub pants along with those gym shoes are what catch his attention. His eyes travel upwards to see a matching top and then when he sees blond hair, he inhales and wonders why this face seems to show up everywhere except in his roster.

Or, he thinks, he's found out exactly why it's everywhere but his roster.

"Atsumu—"

"Aw, c'mon, Aran-kun, don't be mad!" the person whose name Sakusa doesn't care to ever learn laughs. He reaches out a hand, claps it to the back of the taller man. "I apologized, didn't I?! 'sides, now ya know how long it'd take ya to get here in case of an emergency!"

"I already knew that! I didn't need you _and_ Osamu to test me at three in the morning!"

"We didn't know it was that late!"

"We're in the same time zone, Atsumu! We— _we live in the same apartment building!"_

"Keep yer voice down, Aran-kun, yer attractin' attention…"

Aran looks how Sakusa feels on the inside.

He watches _Atsumu_ walk up to the counter, head bobbing as he pulls out his wallet. He pauses; Aran stares at him and even though Sakusa can't hear, the way Atsumu sheepishly grins and Aran brings his hands to his face tells him everything, the way he pulls out _his_ wallet afterwards confirming it. He must've ordered something quick, Sakusa thinks, probably just black coffees because the cashier just turns around to fill two cups and hand both to them.

Aran's pager beeps, the small black device's red light flashing; Atsumu's putting a lid on his coffee when Aran's mouth moves and he nods, waves him off, cheerfully calls, "Save lotsa lives, Aran-kun!" and Sakusa prays that Atsumu's pager also decides to go off.

It doesn't. In fact, it stays noticeably silent and as Atsumu turns, Sakusa realizes that what happens next is _his_ fault because he's still staring directly at Atsumu, which makes eye contact inevitable.

Sakusa considers running. He played volleyball in high school and for the first couple of years in college before choosing to devote himself entirely to statistics; he doesn't work out as much as he used to, but he's still in good shape, and because he'd be running for his life, he thinks that he could outrun Atsumu.

Unfortunately, his brain is thinking that he can't run very quickly in wingtips, that he'll be sweaty and uncomfortable, and that Atsumu's got a head start by already walking towards him. His cup's brought to his lips and the way Atsumu picks up a chair, flips it around and straddles it, Sakusa feels like he wants to die.

The glint in his eyes reinforces this desire.

"Sakusa-sensei," Atsumu greets and smirks. He wiggles his eyebrows. "How ya doin'?"

Sakusa stares at him, squints his eyes at the _student_ who's been attending his thrice-a-week introductory statistics lectures. The _student_ who's wearing a set of scrubs with a stethoscope around his neck and a photo ID clipped to his breast pocket, which makes it impossible for Sakusa to think that he's just dressing up for fun because it's _that face again_ that verifies Atsumu is an actual employee of the hospital.

The _student_ who's been like a ghost except that he shows up everywhere except where Sakusa wants him to and as Sakusa sits here and stares at him, comes to the realization that this student, in fact, is not a student.

"…You lied," he says and Atsumu tilts his head with a smirk.

"Didn't lie, actually," he answers smoothly. "Ya didn't ask the right questions. I studied biochem 'nd ya didn't ask if I was a currently enrolled student." He lifts the hand holding the coffee, taps an index finger to his temple. "Gotta be clever, Omi-kun."

Sakusa desperately wants him to spill his coffee all over himself.

He knits his brow and when Atsumu repeats the nickname, Sakusa has a feeling it's to see if that's what triggers his reaction. It does, which is why Sakusa glares, so Atsumu apologizes. Sakusa's expression relaxes and nods.

Then Atsumu calls him _Omi-Omi_ and Sakusa wants to smack his coffee out of his hands.

"Don't call me that."

"Eh? Kiyoomi's sucha mouthful," Atsumu says and takes another sip of his coffee. "Only mouthful I want of ya ain't just yer name."

Sakusa regrets his whole entire life.

"Mind out of the gutter, Omi-kun, I meant an involved discussion of stats. Besides," Atsumu continues easily as Sakusa's glaring daggers at him, "my cover's blown. Ya know I'm not a student, so don't gotta call ya sensei anymore. Unless, 'course, yer inta that—"

"Stop. Stop talking. Stop talking to me. You're—"

"A resident," Atsumu finishes and Sakusa twitches because he hadn't meant to ask a question, he'd meant to say that he was a nuisance to humanity. He has a feeling Atsumu doesn't care, though, based on the way he smirks. "Pediatric resident. Ya can't hate me, Omi-kun. I save kids."

"I'm supposed to believe that you're a pediatric resident moonlighting as an undergraduate statistics student, spending your little free time attending my lectures for, what, fun?" Sakusa asks. "Lies should at least be believable."

Atsumu's nose wrinkles. "Omi-kun, yer kinda rude. I'm not moonlightin'. I'm _learnin'_."

"Learning?" Sakusa echoes, tone as flat as his expression. In contrast, Atsumu's brow quirks, coupled with a cheeky grin that persists even when he takes another sip of his coffee. "They let you practice medicine when you don't know basic statistics?"

"Hey, never said I didn't pass it 'cause, ya know, it _is_ a requirement for med school," Atsumu retorts. "Just though a refresher would be nice and it happens that yer lectures are durin' lunch. Ya have lotsa seats to spare, too. Guess even a professor like you can't convince everyone to show up. Ya didn't seem to mind the Oikawa kid."

Sakusa decides to ignore the _professor like you_ because even if he's not a student, Sakusa does not want to engage in anything that could be interpreted as flirting with Atsumu.

"I had him enrolled," Sakusa says, frowns. "I'm surprised you remember his name."

"Course I do," Atsumu shrugs. "I used to play volleyball in high school. Kid with the same name as the famous Oikawa Tooru? Hell of a coincidence."

"It's not a coincidence," Sakusa says and Atsumu stares. "He's his nephew. Oikawa-san came by to pick him up for lunch during office hours once and Takeru-kun seemed embarrassed by him."

"Eh?! For real?! And ya didn't tell me?!"

Sakusa stares at him.

"I didn't know you existed. Even if I did, why would I."

"Ain't he in Argentina? Startin' setter for CA San Juan? What's he doin' here?" Atsumu asks and Sakusa grimaces at the way his eyes sparkle when he leans forward. He's regretting sharing what he thought to be harmless information.

"Wedding planning, allegedly," he answers and Atsumu's mouth forms an _o_.

"Engaged? To his boyfriend, right? Iwaizumi-san?"

"I assume that is the case," Sakusa says dryly and closes his laptop, watches how Atsumu blinks and pulls back. "I'm not here to gossip with you. Why are you attending my classes. How do you even have the time."

Atsumu tilts his head, one corner of his lips arching high enough that it's not hidden by his coffee when he takes another sip. "Do ya ever change the intonation of yer voice?"

"No," he says in the exact same pitch.

This is a point where most people start to make excuses to leave, but Atsumu just smirks. "Like I said, Omi-kun, I'm learnin'. Refresher course."

Sakusa inhales to retort, but his phone lights up, successfully diverts his attention. Atsumu pulls out his own phone when Sakusa's eyes drop; it's a text from Komori and while the image preview is too small, the message says _this is Aihara-san's friend!_ and he flips the device upside down.

He can only handle one grievous annoyance at a time.

"Everythin' good, Omi-Omi?"

Sakusa doesn't like how informal these nicknames are becoming.

"Fine," he answers shortly. When he looks up, Atsumu's gazing at him evenly and he clears his throat, glances at the coffee he's still cradling in his hands and scowls. "This is the standard of health you're setting for your patients? Coffee for lunch?"

He realizes that by asking a question he's extending their conversation. He'll end it after Atsumu answers, he thinks, he'll shoo him away and he can get back to work.

"None of 'em are here," he shrugs. Sakusa doesn't like the way Atsumu then smirks at him with his hooded eyes. "What, yer worried 'bout me?"

"I'm worried for our future generation," he corrects, furrowing his brow. "Especially because my lectures are three times a week during lunch time. I hope you're aware I don't allow students to eat in class."

"I'm aware, I'm aware," Atsumu says nonchalantly, waves his free hand. "Ya lookat me all the time, so don'tcha already know I'm never eatin'? I'm really yer best student."

"You aren't even enrolled."

"Right, so you don't even have'ta do anythin' about me. I just show up, learn, and go on my way."

Atsumu smirks at Sakusa's glower that's so prominent that the mask may as well be invisible. "To answer yer implied question, I have Fridays off, so I'm only skippin' lunch twice a week. I just grab somethin' quick on the way back and snack the rest of my shift."

Sakusa frowns. He doesn't like the sound of that and he's sure to let Atsumu know, because he glares at him again. Atsumu rolls his eyes. "Cut me some slack, Omi-kun. I don't have lotsa free time here."

"And yet on one of the days when you _do_ have time to properly take lunch instead of irresponsibly wasting it, you're wasting it annoying me," he says and Atsumu huffs.

"Grabbed an empty wallet on my way out today, what can I say?"

"… _How_."

"So I've got two wallets, right," Atsumu starts, "and they're right nexta—"

"That was a rhetorical question," Sakusa interrupts tiredly and Atsumu sticks out a tongue in an incredibly mature manner. Sighing, Sakusa adjusts his mask and then reaches towards his satchel; Atsumu questions what he's doing and he glares again, uses just one hand to open the bag and reach inside for what he'd been planning to eat.

Taking out the plastic box, he slides it across the table, Atsumu's free hand stopping it seamlessly. "You're not skipping lunch," Sakusa informs him flatly and Atsumu's still staring, eyes going from Sakusa's to the bento several times. "I assume you'll attend tomorrow's lecture, so return it then."

"Eh?" Sakusa honestly expects Atsumu to tease him, accuse him of liking him or something of a similarly immature vein. He doesn't, Sakusa really doesn't like Atsumu, but he also feels somewhat responsible because of his steadfast no eating rule. And, Sakusa thinks begrudgingly, Atsumu treats sick children and there's very little that can paint him in a negative light now.

Sakusa kind of thinks Atsumu might have planned all of this.

"But…" Atsumu's voice trails off and he looks at the lunch again, brow knitting. Sakusa's lips purse from behind his mask; Atsumu hasn't been this quiet in the middle of conversation ever since he met him, wonders what's wrong with him now. "…Ain't this what yer gonna eat?"

"I'll go home and make something," Sakusa answers and Atsumu's still staring at the container. He's set down his coffee in favor of undoing the side clasps, lifts the lid. It's just rice, chicken, and steamed vegetables; it's nothing spectacular, Sakusa says, but informs him that it squarely provides the recommended nutritional intake for a lunch.

Given his brother's in the food business (and because Sakusa grew up with personal chefs so he knows that, objectively, his cooking and presentation aren't quite on par with that standard), he expects Atsumu to make fun of him. But he's just staring at the food quietly and, Sakusa frowns and squints, is he about to _cry_?

Did Sakusa just make him cry?

Sakusa's made people cry without meaning to, but he _really_ didn't think giving someone his lunch would elicit this reaction.

It's not _that_ bad. It looks a little plain, but it's not omitting any offensive odors.

"What's the matter with—"

"Yer sure?" Atsumu asks, his voice so genuine and surprised that Sakusa's taken back for a moment. "Seriously?"

"Yes," Sakusa returns without hesitation because he doesn't see the need for this extreme a reaction. Atsumu stares at him for a moment longer and then his lips curve again, arch into a smile that Sakusa finds himself dropping his eyes from. He hums happily and sets the lid down, takes the included plastic chopsticks and picks up a piece of chicken. "Kids deserve a doctor with a clear mind."

"So ya like kids, huh?"

Sakusa glares. Atsumu grins and Sakusa watches his expression freeze as he takes his first bite; he swallows like it pains him and looks at him warily. "…Omi-kun, yer not a good cook, are ya?"

Sakusa's insulted.

"I'm obviously not a chef," Sakusa says and Atsumu pouts but picks up a piece of broccoli next, "but it's edible. It's better than whatever the cafeteria is serving."

"So that's why ya didn't just lend me some money, huh? Though you'd assume I'd never pay ya back."

Sakusa nods. "That is exactly why I didn't lend you money."

"Won't argue that," Atsumu sighs and Sakusa exhales a bit more than usual, thinks there's no way Atsumu heard that until he looks up with a smirk. "I'm always borrowin' my brother's stuff without askin' him or returnin' it."

"So you're stealing."

"Doesn't count when it's my twin."

"It does count," Sakusa informs but he can tell his words are falling on deaf ears. Atsumu makes a few more quips ( _"ya know food can be healthy and good, right?")_ and Sakusa just glares. He's halfway done and nods when Sakusa tells him he expects it returned and washed when his pager goes off suddenly.

The sound has two reactions:

Atsumu flinching and immediately checking it.

Sakusa realizing that he's still sitting here when he was supposed to nip the conversation in the bud and escape Atsumu's dreaded but persistent company.

"Shit… sorry, Omi-Omi, gotta run," Atsumu says, stands and spins the chair around to push into the table. He recaps the bento and holds it up with a grin. "I'll return this to ya tomorrow. Promise to finish yer best attempt at cookin' me a meal made with love."

"I made it for _myself_ with a normal amount of attention and care—"

"Yeah, yeah," Atsumu says and Sakusa's scowling again. Atsumu holds up a free hand, coffee balanced on top of the plastic. "See ya tomorrow, Omi-kun. Next time make sure to bring two portions, 'kay?"

Atsumu hurries off before Sakusa can process what he's said and by the time he does, Atsumu's slipped back into the hospital, automatic doors closing behind him. His dark brow furrows at being _commanded_ onto a date and Sakusa packs up his laptop, checks his phone after slinging the satchel over his shoulder and heading towards the train to go home.

Komori still hasn't texted him details for dinner and Sakusa answers _do not set me up with him_ so that hopefully Komori will let the subject drop. Atsumu serves one purpose, apparently, because a text that would usually lead to Sakura being on edge and tense the rest of the day is barely able to crack past the cloud of irritation that Atsumu's lingering memories have condensed into.

It's a good thing, Sakusa thinks as he stops at a light, that Atsumu's not a student after all. It's a good thing because if he were, Sakusa would currently be facing the unethical decision of wondering if he can deduct participation points from a student's grade for being insatiably annoying both in and out of a classroom setting.

He's annoying, he thinks, Atsumu's annoying because he makes no sense and the way Sakusa acts around him makes no sense, and it isn't even the sort of unknown that he can begin to formulate a probability density function for. It's the sort of unknown that's just so _what the fuck_ that Sakusa would normally attribute to an error that hadn't been caught before the paper or book he's reading was published. It's not an error that makes sense or can be modeled away, it's the sort of error that exists because of a horrible twist of fate in nature and all Sakusa can do is try to avoid it.

Sakusa takes a breath and adjusts his mask again. Someone accidentally bumps against him and he barely keeps from grimacing, nods at their apology and takes a half-step away. His bag is lighter now and it's just another reminder how he gave Atsumu his _favorite_ bento without thinking twice about it and how he'll have to use a subpar one tomorrow. Why didn't he just lend him some money?, he wonders. It's not like Sakusa's strapped for cash and it's not like he cares about Atsumu.

He doesn't care, except apparently enough to give him his bento and thus disrupt his own planned day by wasting time and making the journey back home in the middle of the day. He doesn't care, except apparently enough so that it overrides even Komori trying to set him up. He doesn't care, except apparently he does and Sakusa's mad because how can he care but not care at the same time?

He frowns behind his mask and fishes his gloves out of his pocket.

He can already tell that this is going to be the least favorite semester in his entire teaching career.

**Notes for the Chapter:**

> writing atsumu's dialogue is hard because 1. i don't actually know how his accent (or accents in general) work and 2. 'yer' is really catchy and i keep finding myself accidentally using it when i'm talking to people
> 
> thank you for reading!! kudos/comments appreciated ♡
> 
> [twitter](https://twitter.com/umebomi)


	3. this isn’t a date

**Summary for the Chapter:**

> “kiyoomi-kun, are you all right? you’re suddenly looking very ill.”
> 
> ushijima has no idea.

Atsumu returns the plastic container and although it's spick-and-span clean, Sakusa washes it again when he's home.

While handing him the box, Atsumu says that Sakusa should probably stick with proofs because he's not very good at cooking. Sakusa informs him that he looks alive and well and that's what matters.

Atsumu tells him that is a very depressing and practical point of view on life.

Sakusa replies that it's realistic and Atsumu's nose wrinkles.

_"As a doctor, I'm gonna prescribe ya a dose of imagination."_

_"You're a pediatrician."_

_"Yer actin' like a kid, so I'm gonna treat ya like one."_

The weeks pass and, besides Atsumu returning his container, he doesn't linger after lectures anymore. Although that's exactly what Sakusa wants, the smirk Atsumu leaves him with before slipping out the door haunts him as he explains the concept of a p-value for probably the four hundred and seventeenth time in his life.

His lectures continue to attract a majority attendance, but Atsumu's one of the few who consistently show up to almost every lecture. Sakusa hates that he notices the rare times he's not there, finds that if he's not at a Monday lecture that chances are he's not there on Wednesday, but will make it on Friday. Sometimes, though, he'll just be late on a Wednesday; he'll look exhausted, bags prominent under his eyes, but he'll show up and as soon as they make eye contact, he'll grin from his corner seat.

The next Friday, Sakusa asks for everyone's attention at the end of class. Almost everyone stills from packing up; a couple students continue to do so, but falter when Sakusa looks directly at them because he has forty seven seconds left and he'll make use of them. Pausing, he pushes his glasses up the bridge of his nose and sighs as he says because he's aware his class is during lunch hour, he'll allow students to eat during lecture. However, he warns and flicks his gaze up sternly, it's a no tolerance policy; if he sees a single wrapper or crumb, the permission will be revoked.

Excited nods wave through the lecture hall, but Sakusa pointedly looks at Atsumu when he says this and he just smirks.

He shows up on Monday with a protein bar and though he leaves without saying anything, when Sakusa passes by his seat on the way out, he notices that it looks as if no one was ever there.

Clean snacking tendencies aside, Sakusa notes that Atsumu continues to not take notes. He's got his little notebook and pen every time and every time Sakusa sees that pen wave, he wonders what kind of a person takes statistics notes in _pen_?

Nobody, apparently, because Atsumu's not taking notes.

He's paying attention, though. He doesn't secretly play on his phone (Sakusa's not stupid, he can tell; no one stares at their lap for ten minutes straight, at least hopefully not in public). He doesn't doze off (Sakusa has _eyes_ and it's so incredibly obvious when he sees a head start to bob). He doesn't even space out (it's a glazed-over look in the eye that Sakusa has seen on Komori's face when he starts talking about his research and it's what Sakusa adopts when Komori talks about how Mao is so good at cooking).

The biggest tell is that whenever Sakusa's eyes sweep that area of the room, their gazes interlock and Atsumu's lips always twitch into a smirk.

He's still not sure why Atsumu's still attending. A part of him had thought that he'd stop but he just _keeps coming_ and Sakusa supposes he hasn't told him _not_ to because, as it turns out, Atsumu's quiet, non-disruptive, and taking just one out of plenty of spare physical seats. He doesn't have a reason to tell him to stop because as annoyed as he is, Sakusa knows that his personal feelings are not a strong enough basis to bar someone from learning. It's still strange, though, Sakusa thinks, why someone with as busy a schedule as Atsumu's continues to attend an introductory lecture that he's learning absolutely nothing new from.

Atsumu makes no sense and Sakusa doesn't like when something doesn't make sense.

"Midterms are approaching."

Sakusa watches Ushijima tear open a packet of sugar and tap it into his coffee, stir a few times before taking a sip. Ushijima is another one of the few people who Sakusa considers to be a genuine friend and who never irritates him; Yachi's in that category as well and the fact that Akaashi isn't is only because Sakusa cannot think of Akaashi without thinking of Bokuto, who he's still convinced hates him a little.

Bokuto insists he meant no harm, that Atsumu really is a good kid and he thought opposites would attract. Sakusa just scowls at him through a video call he's accepted in place of Bokuto showing up at his apartment and possibly never leaving; Akaashi's in the background the entire time, quietly murmurs Bokuto's name when he begins to get frantic and translates when Bokuto's words stop making sense. The call eventually ends with Sakusa accepting that Bokuto had no malicious intent and he says to absolutely _never_ even think about setting him up again and Bokuto nods so vigorously he accidentally slams his head into the table.

Sakusa met Ushijima in middle school at a volleyball tournament and it's the first time he meets someone around his age who displays personal hygiene up to Sakusa's standards. They went to different schools but kept in touch, wound up at the same university together and have both been on campus since. Sakusa's always respected Ushijima, regards him as both a friend and mentor, even if they're in different fields. He's always level-headed; when Komori can (and often is) easily excitable and gets worked up, Ushijima always maintains a calm demeanor and Sakusa thinks that he can talk to him just about anything and have a productive conversation.

He has a productive conversation with Komori about seventeen percent of the time.

Like Akaashi, Ushijima's dating someone whose personality theoretically seems wildly incompatible, but when Ushijima tells him that he and Tendou are engaged, Sakusa's hardly surprised. With both Akaashi and Bokuto and Ushijima and Tendou as examples, Sakusa's conducted a very quick and arguably improper empirical study to conclude that relationships make no sense and he has no time in his life for phenomena that don't make sense. His friends are happy and that's all that matters.

Or something to that effect.

Sakusa nods. "The exam won't be particularly difficult, so the class should do well," Sakusa says. He's craving onigiri today (he has been for a while, actually) but doesn't want to run the risk of seeing Atsumu's face or, worse yet, Atsumu himself. He probably goes there often; even if it isn't to support his brother, Atsumu seems like the sort of person to try and use their identical faces to trick the employees into giving him free food.

Atsumu just gives off that sort of vibe and Sakusa doesn't like it.

He finishes the rest of his rice and presses a napkin to the corner of his mouth. "When I told Kunimi-san the exam would be both multiple choice and free response, he was visibly displeased about having to put more effort into grading than slotting scantrons into a machine."

"It's a large class, isn't it?"

"It is, but he knew that when he accepted the position."

Ushijima nods. Sakusa's pleased that he understands; when he had said this to Komori over the weekend, he actually had the audacity to try and see Kunimi's side and Sakusa piled more carrots into his bowl.

The weeks pass as they always do. Sakusa has too much to do to focus on Atsumu's mysterious and grating presence; his schedule fills up with proposal and draft reviews, preparing lecture notes and writing exams, and overseeing his trio of graduate students. At least his student organization isn't too bad; it's a recreational go club and Sakusa at least thanks Meian for assigning him to something that's lowkey, where he just has to show up and can use the time to keep doing his work. These are college students; it's not as if he has to supervise them for fear of someone eating a stone.

That's what he thinks until he looks up one day to see Hinata Shoyo, who is somehow a graduate economics student, do exactly that because apparently while Sakusa is reviewing a grant proposal, he misses the escalating fight between him and Kageyama, looks over in time to see him definitively swallow something he shouldn't.

Sakusa reports this to Meian, asks if this lack of oversight is enough to warrant someone to replace him.

Meian tells him _no_ and, to make matters worse, Hinata starts to show up at his office hours. He asks him why and Hinata just grins, says he thinks Sakusa's nice.

Sakusa allows this only because Hinata usually brings him a coffee.

"Oh, I believe you've met my TA, by the way. I apologize I haven't introduced you two yet, but he says he enjoys your company."

Sakusa blinks. He's doing a quick scan of everyone he's encountered in the past few weeks; he'd remember if someone mentioned Ushijima, and yet nobody comes to mind. His memories are rife only with students, Komori, and, unfortunately, Atsumu. He looks up to see Ushijima finishing his coffee. "Have I?" he asks with a frown.

Ushijima nods patiently. "Hinata Shoyo."

Sakusa blinks.

"…What."

"Hinata Shoyo," Ushijima repeats with a nod. "I believe he ate one of the stones in the go club you oversee. He says you were incredibly calm when you saw it happen."

Sakusa was calm because he didn't believe that someone actually ate a game piece right in front of him.

"He says he became carried away during an argument with Tobio-kun," Ushijima continues. "I had my doubts about him, but he's quite capable. His focus is on economics and political science because he's hoping to work in foreign diplomacy."

Sakusa isn't sure how he feels about Hinata Shoyo representing Japan in international affairs and is suddenly very afraid for their country's diplomatic future.

Clearing his throat, Sakusa decides that he's trusted Ushijima this entire time he's known him and will just have to take his word, that his first conscious memory of Hinata Shoyo was just an incredibly unfortunate initial impression. Ushijima continues with saying about how insightful he is in his papers and in discussions, despite his demeanor, but it's the sort of personality that puts people at ease.

"I think he has a promising career in front of him," Ushijima remarks.

If he gets hired, Sakusa thinks dryly.

"I actually have to meet with him a bit later, but I did want to bring something up with you first, Kiyoomi-kun," Ushijima says and Sakusa looks up in surprise, sees him gazing at him evenly. "As I've mentioned, Tendou and I will be getting married. We will be sending out our invitations within the next couple of months, but thought it would be fine to let you know that you and Komori-san will each receive an invitation, so you're free to bring a plus one."

The wedding's almost a year away, but Sakusa has a feeling that Komori will bring Mao. She's nice by societal standards, Sakusa thinks; he wasn't particularly impressed, but the way she and Komori smiled at each other the entire night let Sakusa know to expect to see more of her. He hasn't seen Komori this happy with someone since his last boyfriend so, at least, Sakusa's glad for that.

He was getting tired of spending his weekends watching dramas with Komori.

Bokuto and Akaashi will definitely go together and because everyone loves Yachi, she's also invited. Sakusa wouldn't mind spending the wedding talking to her, but she'd mentioned a new girlfriend at their dinner a few weeks ago, and Sakusa thinks it's safe to expect she'll bring her.

Sakusa blinks to realize all the people he actually enjoys spending extended amounts of time will be bringing their own guests and he wonders how he's going to survive this event because he hates making small talk.

He realizes with horror he might have to bring a date.

"Thank you," he says and nods. "I'm not sure if I'll bring someone, but of course I will attend."

"If you'd like me to introduce you to someone—"

"Please don't."

If all of Sakusa's friends keep trying to set him up, he might have none left.

Ushijima nods; he and Yachi have always been the best at immediately respecting Sakusa's obvious and strict boundaries. Komori occasionally tests them, but it's a result of growing up with him; he's able to see when there's a little wiggle room but if Sakusa repeats himself, he knows to stop.

Bokuto tries his best and Sakusa is aware he has good intentions but if it weren't for Akaashi, he has no idea if they'd be able to get along.

"How are you doing?" he asks. "You're in your second semester of teaching now."

"It's going well," Sakusa says. "The transition is certainly difficult."

Ushijima nods. He starts to respond but a chime catches his attention and he pulls his phone out of his pocket and Sakusa's familiar enough to know what the slightly extended stare means. He's already expecting it when Ushijima apologizes and Sakusa just nods. "I apologize, Kiyoomi-kun, but it's later than I thought. Let me know if there's anything I can do. If Kunimi-san wants help grading, I'm sure Shoyo-kun would be more than exuberant to assist. He's quite attached to you."

Sakusa has no idea why.

He nods and Ushijiima begins to pack up his things. The waitress comes by to clear their plates and when she pulls out the check presenter, Sakusa says that he'd like another coffee. She replaces it immediately in her apron and nods, hurries off and Sakusa silently wipes up the crumbs with a napkin, leaving the pile covered near the edge. He's thinking about all the work he should get done this afternoon. Ushijima's managed to publish while establishing himself as a respected lecturer, he thinks, and so Sakusa knows that it's certainly possible. It's all about self-discipline and time management and all he can do is work diligently.

It's if he gets in his own way that he'll be disappointed.

Ushijima begins to pull out his wallet but Sakusa interrupts him and shakes his head. "Congratulations on your engagement, Wakatoshi-kun," he says. "Lunch is on me this week."

He wishes Komori were here so that Sakusa can rub in his face that he _can_ be nice, he just _chooses_ not to be most of the time.

The door opens, draws Sakusa's attention away from Ushijimia's _thank you_. Sakusa can't see the door from where they sit, but they're right in line with the corner that leads to the entrance and he hears a bell and chiming chorus of _welcome!_ The café's of a decent size and while it's busy and every seat is full; the layout is spacious enough that it's just enough white noise for Sakusa to plan on doing some work as he finishes his second coffee.

That being said, even with the white noise of chatter and bustling, the door's bell is bright and sharp. It reflexively has his eyes raising to see who just entered; that's why, he's telling himself, he looked up out of reflex, not because of some cosmic intervention hellbent on ruining his entire life because the person who opens the door and walks in is Miya Atsumu.

Cosmic intervention decides to pull out the chair from under him after kicking the back of his knees because for some reason, Atsumu's eyes immediately meet Sakusa's.

Atsumu blinks and smiles.

Sakusa blinks and wants to die.

"Omi-kun!" he greets and Sakusa immediately looks away, hopes it's enough to make Atsumu leave.

It's not.

"Kiyoomi-kun, are you all right? You're suddenly looking very ill."

Ushijima has no idea.

Sakusa's not sure what Atsumu's intentions are when he comes over; there's a good chance that he just wants to say hello and annoy him before waiting for the next table to open. Unfortunately, what could have been an ordeal that lasts only a few minutes turns into something much worse because Ushijima stands to offer him his seat. Sakusa's glare's lost when Ushijima nods at Atsumu's surprised expression. "Please. I was on my way out and one of my former high school classmates is also a resident; I'm aware there isn't always much time for lunch."

Sakusa hates that his friend is considerate and pleasant.

"Oh, really?" Atsumu asks. "Who's yer classmate?"

"Shirabu Kenjiro."

"Aah, Kenjiro-kun," Atsumu's voice lights up in recognition in a way that Sakusa's sure his expression matches, but he has fingers pressed to either temple and is staring steadfastly at the table. "Yeah, yeah, internal medicine, right? I like 'im. My name's Atsumu, by the way. Miya Atsumu."

"Ushijima Wakatoshi," he answers. "How do you know Kiyoomi-kun?"

"Leave," Sakusa growls, looks up and Atsumu just smiles at him.

"Now, don't be rude, Omi-kun. Ushijima-kun's offered me his seat 'cause he knows how limited my lunches are. Aren't you the one who's also preoccupied with my eatin' habits?"

" _Leave_."

"I'm sure Miya-san doesn't have much time for lunch, so he should be on his way soon," Ushijima reassures and Atsumu's head bobs. "By the way, Kiyoomi-kun, do you go by Omi-kun now?"

"No," he answers immediately and Atsumu grins. Ushijima blinks but nods.

"I sit in on Omi-kun's lectures," Atsumu explains and Ushijima's gaze returns to him. Ushijima looks surprised and Sakusa is so incredibly tired.

"Are you pursuing another degree?"

"Naw, just interested in stats," Atsumu says and Ushijima gives a nod of approval that Sakusa hates Atsumu gets so soon.

"Very admirable for you to use the little free time you have to pursue other unrelated interests," Ushijima says and Atsumu's smile brightens. He turns back to Sakusa and even though he knows that Ushijima has to leave, he still feels betrayed. "Thank you again for lunch, Kiyoomi-kun. I'll see you next week."

He bids a farewell to Atsumu too and when Ushijima's turned the corner, door chiming after a moment, Atsumu takes the previously offered seat, dashes Sakusa's hopes of being left alone. The waitress returns with his coffee and leaves a menu in front of Atsumu with a smile and promises to return. Once she's gone, Atsumu opens the menu and flicks his gaze to meet Sakusa's steely glare. "Funny seein' ya here, Omi-Omi."

"This isn't even close to the hospital," Sakusa says, glowers at him and Atsumu smirks. "Why are you here."

"What, ya think I only exist within a certain limit of the hospital? This place's sandwiches are great and I got some time today."

Sakusa picks up his cappuccino and takes a sip. He could get it to go, he thinks. It would be easy for him to make up an excuse and leave; surely Atsumu doesn't have his entire schedule memorized.

"You can leave, Omi-kun," he hears and blinks, for a moment is paralyzed with fear that Atsumu's actually a mind reader. He lowers his cup to see Atsumu looking at him, shrugging. "Sorry I crashed yer lunch date. If I'd known you were with someone, I wouldn't've come over, honest. I'm sure ya got lotsa professor stuff to do, so I won't keep ya. But if ya wanna stay, got no objections to that either. I always think coffee tastes better outta ceramic than paper, anyway."

Sakusa blinks. His eyes fall to his coffee and then to his satchel, computer still nestled within the leather dividers. With Atsumu here, it's unlikely he'll get much done; he'd been planning on using the entire table to spread out his computer and notes and as annoying as Atsumu is, Sakusa has manners and will allot him half of the space. He should leave, he thinks.

But Atsumu has a point; as much as Sakusa will drink crappy coffee for the caffeine, something about it _does_ taste better out of a proper mug. He's also already taken a sip; it seems a bit excessive to ask for a cup to pour this into just so he can go home, at which point it'll probably be cold. He supposes he doesn't have _so_ much to do that an extra long lunch would truly hinder him.

It's mostly just papers to review and lecture notes to polish up. The most important item on his to-do list is to polish his grant proposal by the deadline because if he secures funding, he can't imagine Meian telling him to spend less time on research. There's still some time, though; he's still got several weeks. He's still waiting to hear back on one he submitted months ago as well; Sakusa isn't one to be sneaky and so Meian is more than aware of what he's doing. He tells him there's no need to rush to submit another proposal when he's waiting on the first one and Sakusa almost answers that he wouldn't need to if Meian would allow him to devote adequate time in the first place.

He manages to bite his tongue, though, because even though Sakusa normally says exactly what he thinks, he understands there are certain politics at play in a work environment.

Sakusa hesitates another moment and sets his mug down, leans back in the chair and shakes his head.

"…I suppose I'll keep you company then," he says and Atsumu beams. The waitress returns and Atsumu orders a simple soup and sandwich combination, adds a latte for himself and a refill for Sakusa. Even with how busy it is, Atsumu's food arrives fairly quickly and besides a polite _ya want some?_ that Sakusa steadfastly declines, they sit in a comfortable silence. Sakusa's checking and replying to emails on his phone, leans back in his chair and sees Atsumu scrolling through his as well, assumes by the way he's laughing that he's either watching a video or on social media. It's nice, Sakusa thinks after a few more emails, to just sit here and relax, sipping on coffee that even Komori might say something nice about.

"Hey, Omi-kun."

This nice atmosphere is ruined.

"Was that yer boyfriend?" he hears and Sakusa looks up, sees Atsumu looking at him evenly. "Ushijima-kun?"

Sakusa blinks. "No," he answers resolutely and to his credit, Atsumu's expression doesn't betray much and he just nods. "We're friends."

"Ah. Good, so I didn't actually crash a date."

Sakusa finds it hard to believe that _that's_ why Atsumu asks, but he's afraid of what Atsumu will ask next if he presses and so lets it slide. Sakusa's eyes return to his email; he's deleting the department announcements that have nothing to do with him and sees a newsletter that Yachi sends out weekly. Tapping into it, he skims the contents and immediately frowns at the congratulations to _three_ of his faculty members on their recently published papers.

"Yer frownin'," Atsumu says, displays an absolutely astounding level of attention to detail.

"Why are you watching me?" Sakusa answers without looking up at him.

"Nobody's texted me, so I'm bored. Yer all I have for lunchtime entertainment."

"I am not lunchtime entertainment," Sakusa snaps and Atsumu shrugs. He watches him pick up a half of his sandwich and take a bite, eye twitches as he tries to recall if he's seen Atsumu wash his hands.

He has to, he thinks, He's a medical professional.

"Whatever. Ya wanna talk 'bout anythin'? I'm basically a stranger, so sometimes it's nice to have an objective party," Atsumu says and Sakusa blinks because he's, unfortunately, making sense.

It's eerie to bridge the Miya Atsumu who annoys him with the Miya Atsumu who's a pediatric resident, that single fact alone bringing with it a slew of heavily supported assumptions about Atsumu's work ethic and intelligence. It's hard for Sakusa to bridge that to the person who's always smirking and who's so annoying to be around, and yet the two paradoxical identities seem to coexist and every once in a while, he'll say something that leans Sakusa's judgment closer to a favorable one.

It's appalling, he thinks.

"No," he says anyway because even if Atsumu makes sense, it doesn't mean Sakusa will do what he says. He lifts his chin scathingly. "Did you wash your hands?"

"Hand sanitizer," Atsumu answers without missing a beat, free hand procuring a bottle from his pocket. "I'm not that gross, Omi-kun. Can I ask ya a question?"

"Is it related to lecture material?"

"Naw. But it's related to yer job," Atsumu says and Sakusa blinks.

That sounds safe.

"All right."

"So, ya wanna get tenure?"

Sakusa doesn't know why he thought this was a safe discussion to have.

His frown deepens. He refreshes his mailbox in hope of an email to give him a solid excuse to leave, but when no one, not even Goshiki with a recent freak out, brings a new notification, Sakusa sets his phone onto the table and crosses his arms over his chest. Atsumu's not looking at him; he's still scrolling through his phone, illuminated screen reflected in his hooded eyes, and finishes his sandwich.

"Why do you ask?" Sakusa returns and Atsumu glances up at him.

"I'm makin' conversation. It's what people do when they get lunch together."

"We didn't get lunch together."

"I'm eatin' lunch and yer sitting across from me with a coffee. I consider this gettin' lunch," Atsumu explains and Sakusa glowers. "Told ya I didn't like to eat alone. I also don't like just sittin' in awkward silence. Like I said, you can leave if ya want."

Sakusa is a practical man. Komori says he's gloomy, which he corrects to _realistic_. It's why he likes statistics; it's why he likes Bayesian statistics because as easy as it would be to think the world is black and white and concrete, that's usually not how it is and the best he can do is work with all the information he can to update the assumptions he operates under.

As such, he doesn't do anything without reason so while he has one reason to leave (Atsumu is annoying), the fact that he has two to say (figure out why Atsumu is annoying and continue their conversation) makes it an obvious choice to remain where he is.

"It's typically the goal of most individuals who pursue academia," he answers evenly and Atsumu hums.

"It's lotsa research, right? Ya like researchin'?"

"Don't ask it like that."

"Like what?"

Sakusa's nose wrinkles. "Condescendingly. Mockingly."

"It's not my problem if that's how ya take my tone, Omi-kun."

"It is because the attitude you give off influences how others react to you."

"I don't care what others think of me," Atsumu answers without missing a beat, looks up and smirks. "Like I said, Omi-kun, you can leave whenever ya want, but if ya stay, I'm gonna talk."

Sakusa hates that he admits his interest is piqued in the apparent clusterfuck of paradoxes he keeps discovering in Atsumu. He doesn't understand him at all and even though he'd usually think it better to focus his time and attention elsewhere, something about Atsumu is intriguing, like an eerily smart rat specimen.

He wants to say this to Atsumu but has a feeling it'll cause more trouble than the satisfaction of his reaction is worth.

"I do like researching," he says finally, arms folding after another sip of his coffee. "I wouldn't have completed a Ph.D if I didn't."

"Enough to wanna do it for yer whole life?" Atsumu asks. He's finished his sandwich by now and Sakusa finds himself focusing on how slowly he's working through his soup. "No offense, but it looks like ya hate teachin'. Yer still good at it, but ya don't look like yer havin' fun. If ya want, we can hire ya."

"We?"

"Yeah, the hospital. Yer a walkin', talkin' billboard for the flu shot."

Sakusa glares and Atsumu smirks. He lowers his spoon and leans back in his chair, head tilting. "Don't make that sourpussed face at me, Omi-kun, I'm callin' it as I see it. Can't ya do plenty of things where yer still researchin'?"

"Why are you so interested in my career path?"

"'Cause ya look miserable everyday up at the front of the lecture hall," Atsumu replies and Sakusa blinks, eyes widening for a moment. Atsumu shrugs. "Like I said, I work with kids. Adults are usually harder to read but yer face is surprisingly expressive. Think it makes up fer yer personality."

Sakusa glares and Atsumu smirks.

"See? Now yer mad."

Sakusa's mad because he wants to glare more but that further proves Atsumu's point. Clearing his throat, he forces his expression to relax, taps his phone and is annoyed that the one time he wants Komori or Bokuto to annoy him, they decide to behave.

"I suppose you've always wanted to be a pediatrician," he says quietly. Atsumu's taken another sip of his soup, followed too soon by his coffee and Sakusa grimaces to think of the flavor combination. "Pretty different from your brother."

"Samu?" he says and Sakusa blinks because the derivation of _Samu_ from _Osamu_ is not difficult at all. "Ah, so you've been to Onigiri Miya? It's really good, right?" he grins and then his expression immediately changes. "Don't tell 'im I said that."

Sakusa's vaguely amused at the way Atsumu's expression goes from bright to a frown at the end. Atsumu leans forward onto his elbow, cups a chin in his hand. "Medicine's not somethin' most people decide to go into last minute, so yeah, been thinkin' 'bout it for a while. I like what I do. Samu likes what he does. My personal trainer _really_ likes what he does."

Sakusa knows that from firsthand experience as well but doesn't want to let Atsumu know that they have a mutual acquaintance because he thinks it'll cement Atsumu latching onto him.

His eyes narrow and he looks to the side, arms crossing. "I like what I do," he says. Atsumu laughs.

"Ya sound like one of my kids when I gotta give 'em a shot."

"I'm not a kid."

"Ya pout like one."

"I'm not _pouting_."

"Sure ya aren't."

Sakusa's glaring before he can think to stop himself and Atsumu's just grinning at him, leans forward and takes another sip of his soup. The smirk relays onto Sakusa's lips when Atsumu's pager goes off; he flinches and the spoon clatters into the bowl, sends bits of splatter flying over his face and scrubs. Atsumu swears and snaps at Sakusa to shut up; he takes a napkin to wipe at his mouth and checks his pager, frowns again and stands. "Ah, shit, sorry, Omi-kun, gotta go. Thanks for lunch. This was a good date. It'll be better next time if we plan it in advance, though."

"What—"

Sakusa blinks as Atsumu stands. "This wasn't a _date_. I'm not _paying_ for you—"

"I'll see ya at class. Midterm's comin' up, so maybe I'll start takin' notes."

"Mid— _you're not a student, Atsumu."_

Atsumu grins.

"Yeah, but yer a professor, Omi-kun. Gonna prove to you that yer good at teachin'."

Sakusa scowls. "I already know I am."

"Maybe I'll fail and take yer ego down a notch."

Atsumu's ruder than Sakusa is because he just leaves after that, doesn't give Sakusa an opportunity to respond. He bows for one more mouthful of soup and hurries off, disappears around the corner, a spring to his step as he checks his pager again. Sakusa just scoffs under his breath and drains the rest of his coffee in one sip; _now_ Koganegawa decides to email him and after skimming to make sure it's not an emergency, decides to leave it for later.

Sakusa waits about ten minutes just to make sure that Atsumu's far and gone; any inclination to do work here is marred by the lingering memory of Atsumu's presence. Securing his satchel, he hoists the strap onto his shoulder and asks for the check, brings it to the front where the hostess smiles at him. He's pulled his mask back on and waits patiently as she taps at the computer, already teased his credit card from his wallet.

"Table four has already been paid for," she informs and Sakusa looks up in surprise to see her charming smile. "I actually have a note for you from Miya-san."

She reaches under her keyboard and takes out a folded piece of paper, _Omi-kun_ ~ written in barely legible writing. After presenting it to him, she asks if there's anything else she can assist with and Sakusa says no, frowning.

"Please have a wonderful day!"

Nodding, Sakusa heads out of the café and passes by a couple who straighten at the sight of him leaving. He's still trying to wrap his head around why Atsumu paid for lunch (now he owes Ushijima a lunch and, he begrudgingly thinks, Atsumu as well) when he steps off the path, stops by a bench situated under a canopy of trees.

He fixes his mask and unfolds the note; almost immediately, Sakusa's eye twitches to see a string of numbers scribbled with a short message beneath.

_Omi-kun, give me a call if you want more career advice ♡_

* * *

Komori gets a call in the middle of the day and though he's drowning in work, when he sees that it's from Sakusa, he picks up immediately because Sakusa doesn't call without warning for no reason.

"Kiyoomi?" he answers with a frown. His free hand hovers over his computer, half-finished code staring at him with a cursor still blinking at the end. "What's wrong?"

"I'm quitting," he hears and Komori's eyes widen. "Let me know if JAXA is hiring statisticians. I don't care about publishing."

"Wait—wait, wait, what?! Kiyoomi, hold on, what're–"

"I am not tenuring on the same campus where Miya Atsumu works."

Komori blinks very slowly.

"...Who… who is Miya Atsumu…?"

**Notes for the Chapter:**

> in your spare time please consider sakuatsu playing animal crossing: new horizons because while they are, by default, a hilarious couple, i believe acnh brings out a whole new potential of fuckery and pettiness
> 
> thank you for reading!! as always, kudos/comments appreciated ♡
> 
> [twitter](https://twitter.com/umebomi)

**Author's Note:**

> sometimes you want to write a fic to explore a character's nuances. sometimes you want to write a fic to explore the intricacies of a certain relationship. sometimes you want to write a fic to explore a certain theme.
> 
> sometimes you want to write a fic because you imagined sakusa in a sweater vest and glasses and it completely fried your brain.
> 
> this might be the most straightforward, least emotionally agonizing thing i've ever done; it's just two idiots being stupid in love. thank you for reading! kudos/comments appreciated ♡
> 
> [twitter](https://twitter.com/umebomi)


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